As David Cameron muses on how this weekend he can snatch the One Nation brand back for the Tories, he won’t be thinking about how to include polarised Northern Ireland. Most of us here were able to unite under the Union Jack to celebrate the Diamond Jubilee or success in the Olympics. In Northern Ireland, the Union Jack flies over the British, Protestant, unionist/loyalist camp, while over that of Irish, Catholic nationalists and republicans is the Irish tricolour. (Just to liven things up, Israeli and Palestinians flags respectively are added in to annoy the opposition.) There, One Nation would be seen as code for a United Ireland.

And now the two communities have embarked on a decade of anniversaries of events that mark their bitter political enmity.

The peace has to be kept by First Minister Peter Robinson and Deputy First Minister, Martin McGuinness. Unlike his predecessor and mentor, the egregious Reverend Ian Paisley, Peter Robinson wasn’t instrumental in kick-starting the Troubles, but he has the unusual distinction of having led an invasion of the Republic of Ireland. Having resigned his Commons seat in 1985 in protest against the Anglo-Irish Agreement, in August 1986 he led 500 or so loyalists across the border into the village of Clontibret, where a garda station and two gardai were attacked. Robinson later pleaded guilty to unlawful assembly and was fined and sent home.

As recently as the late 1990s, McGuinness was one of the ruling cabal running the IRA and Sinn Fein: fomenting angry clashes over Orange parades was a major part of republican strategy.

How soon they forget. Now these sectarian chieftains stand on the sidelines begging their troops to work hand-in-hand to ensure that each community tolerates the commemorations and celebrations of the other. The first big test was last weekend, when more than 30,000 unionists paraded to mark the centenary of the signing of the Ulster Covenant by half a million Ulster people who promised to use all necessary means to resist any attempt by their government to impose Home Rule upon them. Having had problems this summer over small parades, there was much apprehension, but on the whole the day was free of dangerous confrontations.

Looking ahead to future anniversaries variously celebrating violent rebellion or uncompromising resistance, McGuinness explained earnestly: “The last thing that we need on our streets is contention and conflict, and I know from first-hand how damaging that can be to our [specifically his and Robinson’s] efforts to attract foreign direct investment."

The politics of “do what we say, not what we did” are alive and well.

There are some encouraging signs that more and more people are rejecting traditional loyalties. The golfing genius Rory Mcillroy, for instance, from a middle-class Catholic background, is relaxed about declaring himself to be more British than Irish. And many young Protestants are embracing Irish culture. But when parade assemble, banners honouring old warriors flutter in the breeze, and the bands strike up with sectarian and political songs, folk memories of confrontation, anger and betrayal rise up in many a normally peaceable breast.

Labour and Tory top brass may include thugs like Ed Balls and Andrew Mitchell, but as they begin the next round of angry exchanges, Messrs Cameron and Miliband might usefully remember that at least they have the luxury of saluting the same flag and honouring mostly non-contentious anniversaries, and that their rows about One Nation will be mainly about who owns the slogan they both believe they stand for.